The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 11-099170, filed Apr. 6, 1999, entitled xe2x80x9cMethod Of Producing Extrusion Die, Apparatus For Producing The Same, And Extrusion Die Produced By The Methodxe2x80x9d. The contents of that application are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a method of determining at least one dimension of an extrusion die, and an extrusion die produced based on the method.
2. Discussion of the Background
As is obvious from its schematic structure shown in FIG. 1, an extrusion press 10 used for extrusion generally is constructed by a container 11, an extrusion die 12 fixed to one end of the container 11, a stem 13 movably mounted on a pushing ram at the other end of the container 11, and a bolster 16 for fixing the container 11 and the extrusion die 12 through a backer 14 and a die ring 15. An extrusion method is, for example, a hot working method including placing a cylindrical aluminum billet in the container 11 interposed between the extrusion die 12 and the stem 13 and moving the stem 13 to extrude the billet into a product from the extrusion die 12. Most billets used for extrusion are cylindrical but square billets may be used. When a material having excellent hot workability such as aluminum is extruded by the above method, even a product having a complicated shape may be obtained.
The extrusion die used for extrusion has a shape shown in FIG. 2 as an example. The design values of the extrusion die mostly depend on the thickness of an extruded product and typical design factors include a bearing length and a flow guide shape. In this invention a flow guide shape or a chamber shape means absolute shape: that is because shape has the meanings of both size and shape.
The bearing is a part to give friction to an extrusion material for controlling a metal flow and formed at the outlet of the extrusion die. For example, in the case of a solid (product having no hollow portion) extrusion die shown in FIG. 2, the bearing is a portion where an extrusion material is extruded (in the figure, the inner wall of a die hole corresponding to the cross-section of a product). The purpose of forming the bearing is to form an extruded product having a desired shape. Stated more specifically, by changing the wall length of a bearing at each portion, a metal flow is controlled making use of friction at the time of extrusion to mold in an extruded product having a desired shape. That is, by changing the length of a part to give friction to a metal according to the shape of a product, a metal flow is controlled properly and a product of high quality which cannot be bent by metal flow or the like is extruded.
Generally speaking, when there is nonuniformity in the thickness of a product, the metal flow rate tends to be higher in a thick portion than in a thin portion at the time of extrusion. Therefore, the wall length of a bearing of a portion corresponding to the thick portion must be designed relatively larger than the wall length of a bearing of a portion corresponding to the thin portion. Thus, the determination of the wall length of the bearing is one of important factors that affect extrusion results in terms of the size and shape of an extrusion material.
A description is subsequently given of a general method of determining the wall length of a bearing.
Points (points along the die opening for calculating the wall length of a bearing) for calculating the wall length of a bearing on an opening (die hole shape) of a die are first determined. For example, when a product has a sectional shape as shown in FIG. 3, two different points (points A and B) on the reference line of the bottom portion of the section are selected. Thereafter, thicknesses at these calculation points are measured and the wall length of the bearing is calculated using the bearing wall length calculation equation of each designer. A die having the calculated bearing wall length is produced and extrusion is carried out using this die. Stated more specifically, based on the thickness of 40 mm at the point A and the thickness of 15 mm at the point B, the wall length of the bearing between points A and B is obtained.
Even when the measurement of the thickness of a product is carried out by each designer independently, in the case of a straight angular shape surrounded by parallel straight lines as shown in FIG. 4, since the shape is simple and a single design standard can be applied, differences among the concepts of designers and the methods of applying design standards are rarely occurred.
However, since extruded products are various in shape, there are differences in thickness measurement among designers with the result that dies which are designed differently may be obtained. For example, in the case of a product having a shape shown in FIG. 5, definition xe2x80x9caxe2x80x9d and definition xe2x80x9cbxe2x80x9d are conceivable for the determination of thickness at point C in the figure and there is a difference in the measurement value of thickness according to differences in concept among designers and design standards such as thickness measurement method and the like.
Since the shape of the opening of an extrusion die is complicated and various, in the present situation in which a reference line is used to measure the thickness of an extrusion material as the basis of the design of a bearing or the measurement of thickness depends on the judgment of each designer, the step of making a bulky manual describing a huge number of product shape patterns and minute rules is required to reduce differences in thickness measurement method among designers.
When a die opening is shaped like an ameba having no symmetry at any portions, xe2x80x9cthicknessxe2x80x9d itself cannot be defined, thereby making it impossible to design a bearing based on predetermined standards by a conventional bearing design method.
Meanwhile, CAD has been frequently used for the design of an extrusion die in recent years. Even when CAD is used, product thickness measurement methods are classified by the shape of a die opening and further complicated rules are incorporated into a CAD program, a huge number of program production steps and a huge number of maintenance steps are required to produce a program which covers all kinds of products having thousands of different shapes. Further, since thickness itself cannot be defined even by using CAD incorporating design standards based on conventional design techniques, the above opening having a completely unsymmetric shape cannot be incorporated into a CAD program, thereby making it impossible to automate the design of a die.
Moreover, since there is such a case as lack of some patterns or rules, a method of defining the measurement of the thickness of a product according to the shape of a product in an one-to-one correspondent manner is necessary even if any type of the product shape is given.
The following two typical methods have been used to define thickness.
The first method (1) is, as shown in FIG. 6, to draw inward a perpendicular or normal to an element (line segment or circular arc) belonging to a bearing wall length calculation point D (D1, D2, . . . ) on an opening from the calculation point D, obtain an intersection point E (E1, E2, . . . ) with an element on the opposite side, and define the distance between the intersection point E and the bearing wall length calculation point D as thickness.
The second method (2) is, as shown in FIG. 7, to provide a predetermined reference line on the under surface of extrusion for the shape of a product, draw inward a perpendicular to the reference line from a bearing wall length calculation point F (F1, F2, . . . ), obtain an intersection point G (G1, G2, . . . ) with an element on the opposite side and define the distance between the intersection point G and the bearing wall length calculation point F as thickness.
According to the above methods, it is possible to define thickness based on a specific method but there is a problem in fact. Stated more specifically, when the thickness of a product of FIG. 8 is measured by the method (1), the wall length of a bearing is longer at point K than at point H and the wall length of the bearing changes abruptly.
The method (2) has such a problem that the value of thickness defined differs according to how to take a reference line. For example, although a product shown in FIG. 9 is similar in shape to a product shown in FIG. 7 (they differ only in the existence of a projecting portion), they differ in the value of thickness defined because they differ in reference line.
That is, various thicknesses are obtained according to how to take a reference line.
Therefore, in these bearing design methods, even when products have almost the same shape, if they differ only in the shape of a minute portion, extrusion dies having different bearing wall lengths are produced. Further, when the thickness of a product changes abruptly, the wall length of a bearing cannot be changed smoothly according to the shape of a die opening and the shape of a product may not be stabilized.
Moreover, in the case of a completely unsymmetric ameba-like shape, a reference line cannot be drawn, and in the conventional bearing design method, the size of a bearing cannot be determined based on predetermined standards. The same problems as above are encountered even when a completely unsymmetric portion is a part of a product figure.
As an important factor of an extrusion die that affects extrusion results in terms of the size and shape of a product, a flow guide or chamber is named. The flow guide or chamber is one of means of controlling a metal flow and formed similar in shape to a product in an extrusion die to control a metal flow in order to make up for limitation to the control of a metal flow with a bearing, thereby being capable of stabilizing the shape of a product of an extrusion material with these.
The term xe2x80x9cflow guidexe2x80x9d as used herein is mainly used in the case of a solid die and includes a feeder or baffle plate formed to a predetermined shape as a unit separate from a well formed in an extrusion die and an extrusion die. They are generally defined as xe2x80x9cflow guidexe2x80x9d.
In the case of a hollow die, an extrusion material passes through a metal welding chamber called xe2x80x9cchamberxe2x80x9d and a metal flows into a bearing. Therefore, the metal welding chamber has the same function as that of the flow guide.
However, as for the design of the flow guide or chamber, an appropriate design method for obtaining an appropriate product shape is not established like the design of a bearing. Design standards based on the judgment or past experience of each designer are selected, and a design method for determining the shape of a flow guide or chamber for a product having a desired shape in an one-to-one correspondent manner is not established, which is one of the reasons why the shape of an extruded product is not stabilized.
According to one aspect of the invention, a method of determining at least one dimension of an extrusion die includes determining a plurality of reference points on a contour of an opening of the extrusion die. Sizes of a plurality of figures with same shapes corresponding to the plurality of reference points are determined. Each of the plurality of figures is inscribed in the contour of the opening and has at least one axis of symmetry. Each of the plurality of figures contacts each of the plurality of reference points and at least one another point on the contour. The at least one dimension of the extrusion die is determined based on the sizes of the plurality of figures.
According to another aspect of the invention, a method of producing an extrusion die includes determining a plurality of reference points on a contour of the opening of the extrusion die. Sizes of a plurality of figures with same shapes corresponding to the plurality of reference points are determined. Each of the plurality of figures is inscribed in the contour of the opening and has at least one axis of symmetry. Each of the plurality of figures contacts each of the plurality of reference points and at least one another point on the contour. The at least one dimension of the extrusion die is determined based on the sizes of the plurality of figures. The extrusion die is produced based on the at least one dimension. According to further aspect of the invention, an extrusion die includes an opening through which material is extruded; and at least one portion having a dimension determined based on sizes of a plurality of figures with same shapes. Each of the plurality of figures has at least one axis of symmetry and is determined corresponding to each of a plurality of reference points which are determined on a contour of the opening. Each of the plurality of figures is inscribed in the contour of the opening and contacts each of the plurality of reference points and at least one another point on the contour.
According to yet another aspect of the invention, a flow guide for an extrusion die which has an opening through which material is extruded includes a portion having a dimension determined based on sizes of a plurality of figures with same shapes. Each of the plurality of figures has at least one axis of symmetry and is determined corresponding to each of a plurality of reference points which are determined on a contour of the opening. Each of the plurality of figures is inscribed in the contour of the opening and contacts each of the plurality of reference points and at least one another point on the contour.
According to yet another aspect of the invention, a chamber for an extrusion die which has an opening through which material is extruded includes a portion having a dimension determined based on sizes of a plurality of figures with same shapes. Each of the plurality of figures has at least one axis of symmetry and is determined corresponding to each of a plurality of reference points which are determined on a contour of the opening. Each of the plurality of figures is inscribed in the contour of the opening and contacts each of the plurality of reference points and at least one another point on the contour.
According to further aspect of the invention, an extrusion die designing apparatus to design an extrusion die having an opening through which material is extruded, includes a reference point determining device, a figure size determining device and a dimension determining device. The reference point determining device is configured to determine a plurality of reference points on a contour of the opening of the extrusion die. The figure size determining device is configured to determine sizes of a plurality of figures with same shapes corresponding to the plurality of reference points. Each of the plurality of figures is inscribed in the contour of the opening and has at least one axis of symmetry. Each of the plurality of figures contacts each of the plurality of reference points and at least one another point on the contour. The dimension determining device is configured to determine at least one dimension of the extrusion die based on the sizes of the plurality of figures.
According to yet another aspect of the invention, an extrusion die designing apparatus to design an extrusion die including an opening through which material is extruded, includes reference point determining means, figure size determining means and dimension determining means. The reference point determining means determine a plurality of reference points on a contour of the opening of the extrusion die. The figure size determining means determine sizes of a plurality of figures with same shapes corresponding to the plurality of reference points. Each of the plurality of figures is inscribed in the contour of the opening and has at least one axis of symmetry. Each of the plurality of figures contacts each of the plurality of reference points and at least one another point on the contour. The dimension determining means determine at least one dimension of the extrusion die based on the sizes of the plurality of figures.
According to yet another aspect of the invention, an extrusion die producing system to produce an extrusion die having an opening through which material is extruded, includes a reference point determining device, a figure size determining device, a dimension determining device and a machine. The reference point determining device is configured to determine a plurality of reference points on a contour of the opening of the extrusion die. The figure size determining device is configured to determine sizes of a plurality of figures with same shapes corresponding to the plurality of reference points. Each of the plurality of figures is inscribed in the contour of the opening and has at least one axis of symmetry. Each of the plurality of figures contacts each of the plurality of reference points and at least one another point on the contour. The dimension determining device is configured to determine at least one dimension of the extrusion die based on the sizes of the plurality of figures. The machine is configured to produce the extrusion die based on the at least one dimension.
According to yet another aspect of the invention, a computer readable media is provided for controlling a computer to perform the steps of determining a plurality of reference points on a contour of the opening of the extrusion die; determining sizes of a plurality of figures with same shapes corresponding to the plurality of reference points, each of the plurality of figures being inscribed in the contour of the opening and having at least one axis of symmetry, each of the plurality of figures contacting each of the plurality of reference points and at least one another point on the contour; and determining the at least one dimension of the extrusion die based on the sizes of the plurality of figures.
The above and other objectives, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.